Project Summary: Neuropeptides are key components of modulation across the central nervous system. These short peptides are released from neurons and non-neuronal cells and have powerful modulatory effect on neuronal activity leading to changes in sensory perception, motor output and complex behaviors. Currently there are no experimental tools that can manipulate the release and functions of these important neuromodulators with high spatial and temporal resolutions. As such, the main objective of the proposed project is to develop optogenetic approaches to inhibit the release neuropeptides from neurons without disrupting the release of non-peptide neurotransmitters. In addition, we will also develop an improved approach to suppress the release of all synaptic vesicles non-selectively. To achieve these goals, we will use photosensitizing fluorescent proteins in combination with chromophore assisted light inactivation (CALI) and light induced protein dimerization (CRY2/CIB1) to disrupt the release of secretory vesicles from neurons. By targeting these proteins to vesicles containing neuropeptides, we will be able to achieve the selective disruption of the release of neuropeptides without affecting synaptic transmission. These tools can be used to selectively turn off the release of neuropeptides at a specific region, at a specific synaptic connection or onto specific cells with unprecedented temporal resolution. We expect these tools to drastically change the way we, as a community of neurophysiologists, approach the study of neuromodulation, eventually gathering new knowledge to understand the underlying circuits for human thoughts, feeling, and actions and its disruption in neurological disorders.